Mechanism of Hard Rock Static Blasting-induced Crack Expansion

Abstract

Abstract How to deal with hard rock cheaply and safely is a pressing issue in today's coal mining. Weakening fractures in hard rock have always been a significant concern in China's coal mine engineering. In this study, the mechanism of a crusher fracturing hard rock is examined from a mechanical standpoint based on the static crusher component action and the expansion mechanism of the hydration reaction. It is assumed that single-hole fracturing is divided into three fracturing stages: the microfracture stage, the fissure development stage, and the rupture stage. It was determined that the expansion pressure of SCA increased with the increase in hole diameter under the hole diameter range of 30 mm-45 mm, and the range of the expansion pressure was 43.5 MPa-75.1 MPa; the reasonable use of SCA was summarized; and the expansion and fracturing properties of SCA were quantitatively analyzed based on the expansion pressure test and single-hole specimen fracturing experiments; Three fractures, typically in the form of "D-type damage, were the hallmark of expansion cracking in single-hole specimens. SAC cracking began later, but the breaking rate was still rather significant. PFC2D was used to mimic the expansion fracturing of a single-hole specimen without peripheral pressure, which matched the experimental fracturing result and demonstrated the viability of using PFC to replicate SAC fracturing. Analysis of double-hole specimens with varying hole diameters, hole spacings, and circumferential pressures under expansion revealed that the hole diameters were positively correlated with the cracking effect, the hole spacings and circumferential pressures were negatively correlated with the cracking effect, and the hole diameters were also positively correlated with the crack extension and distribution characteristics. Combining the findings from experimental and numerical research, it can be said that the pore size of SCA plays a dominating role in the fracturing impact and that the second largest influences are pore spacing and surrounding pressure.